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zorro
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# Posted: 19 Jun 2025 11:06am - Edited by: zorro
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So here is my system;
3 x 340W Panels
1 x 1500W Samlex Pure Sine wave Invertor
1 x MPPT controller
8 x 6V 230amp batteries (Lead acid.....old school)
I have a generator that back feeds the batteries to charge when needed
Batteries are not holding a charge and even when they get to say 73%......drop quickly, getting only to a max of 73% charged with a 24.8 voltage reading
Just used a Hydrometer - reads 1150
No visible damage or swelling and water/acid levels have always been maintained
So looks like my batteries are in trouble??
So without changing everything, what would my best option be here in terms of batteries?
I could increase the invertor to say 3000W and a bit more storage capacity would be good in the batteries
These are my current (x8) batteries;
https://www.lowes.com/pd/Deka-6-Volt-448-Amp-Golf-Cart-Battery/50183775
Any suggestions without breaking the bank?
Thanks
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MtnDon
Member
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# Posted: 19 Jun 2025 01:16pm - Edited by: MtnDon
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Quoting: zorro I could increase the invertor to say 3000W
Do you really need the extra capacity?
You didn't specify the battery configuration. 12 volt? 24? ???
What make/model of MPPT charge controller do you have? It may or may not be compatible with LFP batteries. Also, if you are changing the system voltage, it may or may not be possible to do so. Many can do 12, 24 and some do more, but we don't know right now.
Also, when using the generator to charge what battery charger make/model do you use. That too needs to be verified if it is compatible with LFP batteries (if you switch).
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groingo
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# Posted: 19 Jun 2025 01:56pm - Edited by: groingo
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How old are your batteries, have they been kept in a climate controlled area or outside, are you running in off grid completely or supplimental power, how many KWH a day do you require from them, do you regularly run below 11 volts....sounds like it is LFP time and wouldn't sweat the inverter at this time.
With LFP you get a lot more bang for the buck, one LFP will easily do the work of two floodeds and they recharge much faster and as you know last much longer. When time comes for LFP go for a name brand with REAL Support in the US not some Pigchdong4874 brand with email support!
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zorro
Member
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# Posted: 19 Jun 2025 03:56pm - Edited by: zorro
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Sorry, some further details
I think it was likely my own fault by putting too much on the batteries and has maybe damaged them
Would taking them "out" and putting them on a battery charger maybe help??
All batteries are outside in a "box" during winter (sub zero up in the Adirindacks), but I ALWAYS makwe sure they are fully topped up and fully charged before i leave for the winter
Anyway, originally set up 4 years ago, only running some LEDS lights, a small refrigerator and cell phone/laptop charging - everything was fine...........till this year
This year I added a TV (2/3 hours per day), Starlink (7am - midnight) and a small freezer (24/7) - that is when the problems arose...........likely too much demand on the batteries
So essentially, that is what i need to be able to run, which leaves me thinking i need more battery capacity that what I have
Current system is as follows;
3 x 340W Panels
1 x 1500W Samlex Pure Sine wave Invertor
1 x MPPT controller
8 x 6V 230amp batteries (Lead acid.....old school)
1 x Battery charger connected to the generator for back feeding
Charge Controller
(Supports charging lithium batteries, gel batteries, sealed batteries and vented batteries)
Max Input power - 1600W/24V, 2400W/36V, 3200W/48V
https://envoltage.com/products/solar-charge-controllers/ev-ml4860-mppt-solar-charge-c ontroller-2/
Battery Charger
(Charges AGM, lead acid, GEL and LiFPO4 batteries. Power supply up to 75 amps at 12Vdc or 37.5 amps at 24Vdc.)
https://www.amazon.com/dp/B07N1K43NQ?ref_=ppx_hzsearch_conn_dt_b_fed_asin_title_30&th =1
In terms of the 1500W invertor - only reason I suggested upgrading that was for the coffee machine and vacuum that my wife uses - but if I can get away without that for now and concentrate expenditure on the batteries, i would do that and worry about the inverter next year
So I think I need more battery capacity at a minimum, to run everything I have now - so recommendations on type/capacity/supplier would be great..............and is there anything else needed for LFP batteries for example (assuming my equipment supports those)
Would something like this work (or is this cheap Chinese junk and should be avoided)
https://shorturl.at/Pm5z4
OR
https://shorturl.at/TYpJm
Couple of points;
Batteries will be left at the cabin all over the depths of winter - so can they cope with that extreme weather (if I come back after winter and my batteries have frozen, my wife will likely kill my and place me in the septic system!!)
Will my Inverter and Charge controller work with them on a plug n play basis
Apologies for all the info - just trying to get the best recommendation from guys that know what they are talking about..........and I am no expert unfortunately
One other thought - how do I know it is NOT the charge controller which is faulty and perhaps not charging the batteries fully?
Thanks
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Brettny
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# Posted: 19 Jun 2025 04:09pm
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I also have golf cart batteries and there alot outside in central NY. I also run a fridge, lights and have for 4yrs. However I do leave my charge controller hooked up all winter and when I leave at any time of year my inverter is off. This year I added a mini split and they seam to take that load as expected.
How are you getting the % charge? Did you use the hydrometer in every cell? It could be a single cell bring the whole bank down.
In today's age lead acid costs more than lithium. I would get heated lithium cells and find a place for them in the cabin. I plan on putting a 3 pack of server rack heated lithium under my stair landing to the second story. And no lithium still isnt cheap but you get alot more capacity for the price.
With that being said my 4yr old golf cart batteries arnt really showing signs of failing. But I'm only there one weekend a month for 2 days so that's about 100 cycles. Alot of that is due to my loads being off when I'm not there.
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zorro
Member
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# Posted: 19 Jun 2025 04:18pm
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I tried 4 different batteries with the hydrometer and all showing around 1150...........i never tried every cell across all the batteries
There is nowhere inside they could go - I could easily build an outside "battery box/shed" with some insulation and raise them off the ground, but it will still be subject to the brutal winters here
Interestingly, today, it is bright sunshine and warm, the panels are outputting 33.6V/665W and the batteries go to 83%
As soon as the sun goes behind a cloud, batteries start dropping almost immediately - within 5 minutes go from 83% to 66%
The % charge I am getting from the CC screen
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Brettny
Member
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# Posted: 19 Jun 2025 04:36pm
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Quoting: zorro he % charge I am getting from the CC screen
Check every cell..
Spend $100 on a victron smart shunt before you change any hardware. I suspect the CC is going by battery voltage and with lead acid this is a prety poor way to try and get % capacity.
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zorro
Member
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# Posted: 19 Jun 2025 05:24pm
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Ok - will need to look into the victron shunt
Just checked all 24 cells
22 cells read around 1150 - 1175 max
2 cells read as shown below, around 1225
[img=null]null[/img]
Currently almost nothing running in the camp other than the small refrigerator i have had for 4 years
Sun is gone and awaiting thunderstorms
Battery reading according to the CC has gone from 84% down to 51% in 3 hours, with almost nothing running
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gcrank1
Member
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# Posted: 19 Jun 2025 11:09pm
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Your bat-bank is only as good as its worst battery, it will drag the rest down.
You must number the bats, and number the cells in each and test/record ALL that so you can determine which is the culprit.
As far as killing them....Lead Acid bats have just only so many charge/discharge cycles, faarrr less than LFP.
GC bats are made more heavy duty than marine/rv bats and can take more deep discharges BUT if you regularly discharge to, or below, 50% you kill them much faster; LFP NO Prob.
My target with LA was 30% discharge for long life and only below that to max 50% if necessary. Then on a good solar day to be recharged full by 1pm.
If you increase your usage you have to increase the bat-bank size, which then means (often) increasing the array size and maybe the scc to meet the recharge target.
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zorro
Member
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# Posted: 20 Jun 2025 02:34am
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I think that is the BIG issue
I did increase usage by adding electrical items, but never increased the battery bank - I think I have damaged the batteries as a result
When I checked all 28 cells, 26 of them were bad
I am not expert so don’t know if I can take all the batteries out and try to “recharge” them using a battery charger - no idea if that will work or not
If not, then I really need to consider what options are in terms of Lithoum batteries
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Brettny
Member
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# Posted: 20 Jun 2025 08:12am
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You could try a desilphater..I'm spelling that wrong. Try a victron shunt before replacing the batteries. It can help you learn your useage and when you should be turning on the generator to charge the batteries.
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gcrank1
Member
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# Posted: 20 Jun 2025 09:24am
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The big 'damage' may have been done by not getting them recharged back to 100% (or maybe 95% on well used bats) most of the time.
LA bats of any type want to be kept fully charged.
My 'smart charger' supposedly has a 'reconditioning mode' that comes on after they get to top charge. A few of my LA bats have stayed on that mode far longer than others when I initially used the charger on them all. Most seem to hold a charge better after a few sessions like that (I take all my non-essential bats from equipment out for winter and store in basement then rotate charging so all get a full charge at least once a month. My bat life spans have increased)
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zorro
Member
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# Posted: 20 Jun 2025 09:36am
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Agreed
Thanks guys
This morning when I woke up, they were at 33% and 23.4V
Clearly that is not good!
I will take them home next week to try to charge them and desulphate them - at this point they likely can’t get much worse than they are
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zorro
Member
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# Posted: 20 Jun 2025 11:06am
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If my batteries do need to be replaced, can anyone give me some recommendations on replacements
Would 2 of these work with my current CC and Inverter and provide greater storage capacity
https://shorturl.at/TYpJm
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travellerw
Member
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# Posted: 20 Jun 2025 01:02pm
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Quoting: zorro Would 2 of these work with my current CC and Inverter and provide greater storage capacity https://shorturl.at/TYpJm
First, we don't have enough information to comment. Model numbers would be required for inverter, MPPT controller and battery charger. Without those its a completely a guess (would probably work, but not optimized as the mppt and battery charger require adjustable voltage to work their best with LiFePO4). I suggest you get the model numbers and then download the manuals to confirm they can work with LFP batteries.
Second.. Its really a crap shoot on purchasing off brand chinese LiFePo4 batteries. Even if the cells are a quality brand, the BMS is a whole other thing. Will Prowse does some decent reviews on his Youtube channel, but still leaves things out. He is not an electrical engineer and doesn't look at the component level. Not his fault as that would be too deep for most of his viewers. However, while his reviews may be favourable, he has no way to verify the longevity of the batteries. They may last years, or they may die quickly. If they do die, many Chinese off brands don't really have a warranty.
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gcrank1
Member
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# Posted: 20 Jun 2025 02:30pm
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Heated LFP will be self depleting from the heater(s) and the recharge system must be up to the task of keeping them topped up in all weathers while unattended.
It has happened that a system has failed for whatever reason, the heater runs the bats down to the LVD and then what....
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zorro
Member
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# Posted: 20 Jun 2025 02:43pm
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I was thinking about the cold weather - generally, we leave the camp for the season around Thanksgiving and then not back again till the spring
We could easily take them with us at that point rather than leaving them here over the winter, to prevent any extreme cold impacting them - so that would not be an issue
For info, here is the detailed breakdown of my system and components and info I can find ......
Here is the detailed info on my system;
24V System
3 x 340W Panels
1 x 1500W Samlex Pure Sine wave Invertor
1 x MPPT controller
8 x 6V 230amp batteries (Lead acid.....old school)
1 x Battery charger connected to the generator for back feeding
Charge controller - ML4860 (60amp)
https://shorturl.at/90GO4
Versatile Voltage Compatibility: Automatically detects and supports 12V, 24V, 36V, and 48V battery system
Designed with flexibility in mind, the ML4860 supports a wide range of battery voltages and types, including sealed, gel, flooded, and lithium batteries
Inverter
Samlex Pure Sine Wave 1500W (PST 1500-24)
https://shorturl.at/mWGWn
Battery Charger
AIMS Power (CON120AC12/24VDC)
https://shorturl.at/kdufN
Large charging capacity design (75 Amp at 12Vdc; 37.5 Amp for 24Vdc) charges a 100 amp hour battery in under an hour up to 90% charge Listed to UL 458 and CSA 22.2 NO. 107.1
Charges AGM, lead acid, GEL and LiFPO4 batteries. Power supply up to 75 amps at 12Vdc or 37.5 amps at 24Vdc.
I dont have anything else in the system
So it looks like they all support Lithium batteries and are 24V compatible - all are around 4 years old and appear to function normally
Does this help in terms of battery selection/type?
I need a battery system which provides more storage capacity than what my current 8 x 6V, 230Amp battery currently provide
Any suggestions?
Thanks
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MtnDon
Member
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# Posted: 20 Jun 2025 03:11pm - Edited by: MtnDon
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Two of these.
https://www.us.sokbattery.com/product-page/sk24v150ph-24v150ah-battery-built-in-heate r-bluetooth-victron-can-comms
LFP charge more rapidly than lead-acid; for example, even with everything else the same you get faster charging from your solar.
You may already be aware that LFP can be safely discharged more deeply than lead-acid. You can actually use 80% or more of the rated capacity unlike lead-acid.
Are the charge controller setting user programmable down to a tenth of a volt, or is there just an LFP preset that can be selected?
We have used an SOK 24 volt 100 amp battery for two years and have been quite happy.
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paulz
Member
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# Posted: 20 Jun 2025 03:22pm
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Another Lfp vote. I’ve dealt with two LAs this week, one my generator and one my old hot rod. Both been sitting and both corroded terminals. There are reasons LA are needed but Lfp if possible.
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Brettny
Member
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# Posted: 20 Jun 2025 05:00pm
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Quoting: gcrank1 Heated LFP will be self depleting from the heater(s) a
That's not really how they work. What they do is they use incoming power from the CC to heat them self..then when up to temp they will charge.
I would highly doubt your current battery charger would work with lithium batteries unless the voltage is selectable. If your going to swap out the inverter too just get a inverter charger. Most will have some type of transfer switch built in too.
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MtnDon
Member
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# Posted: 20 Jun 2025 05:58pm - Edited by: MtnDon
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Quoting: Brettny That's not really how they work. What they do is they use incoming power from the CC to heat them self..
Yes. The BMS senses temperature and won't allow charging when too cold. The BMS will direct incoming charge current to the heater. When the BMS senses a warmer temperature the current is directed to charge the battery. No sun, no charge.
I had a quick look at the user manual for the AUMS charger. It's LFP setting has fixed voltages: both bulk and float at 28.8. That's not going to be the best for battery life. For example SOK recommends 27.6 volts for float on 24 VDC battery. (13.8 on 12 VDC)
You should the solar charge controller too. For best LFP life any charger should allow the charge/float voltages to be custom set to tenths of a volt.
Most good LFP should also have a bluetooth app
Also, some chargers are too 'smart'. Some will not charge a battery unless they first sense a voltage. The BMS in many LFP batteries basically shut down after a period of no charging or discharging. This is to prevent the battery being discharged from the power the BMS uses when it is sitting idle, but waiting for something to happen. Think of this like the standby loss of an idle inverter.
There are good quality chargers (AC & solar) that will work on a LFP battery with a sleeping BMS. And there are ways to trick the battery BMS to wake up. Partly depends on how easy, how plug'n'play you want this to be.
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MtnDon
Member
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# Posted: 20 Jun 2025 06:01pm
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Screenshot from AIMS manual
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gcrank1
Member
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# Posted: 20 Jun 2025 09:03pm
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Guess I was thinking of the folks who have used aux heat 'blankets' as bat warmers. Since I decided to just take my LFPs home for winter (I could leave an old, good AGM hooked up for an occasional trip in) I stopped paying attention to LFP bat heating technology.
So Ive learned something again here today! 
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travellerw
Member
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# Posted: 20 Jun 2025 09:23pm
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I think a quick "sum up" may be in order.
1. LFP batteries are not equal to FLA (no matter what the sales brochure says). You WILL need to educate yourself as to the particulars of LFP.
2. Adjustable voltages are "advisable". An LFP or Lithium setting is not recommended. You want fully adjustable voltages.
3. Heated batteries are great if you want to "CHARGE" them in freezing temps. If you plan to winterize and take the batteries, then don't bother with heated unless you get a great deal.
4. Not all LFP are created equal and its not just the cells. BMS is a major part of the battery as if it dies, the battery is effectively dead even though the cells are fine!
5. 6 times out of 10, you will need to replace multiple components (MPPT, battery charger or inverter) if you switch to LFP from FLA.
Now my opinion.
Is it worth it?
Yes, even if you have to replace multiple items. LFP is a game changer. Especially if you don't charge them in cold temps.
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Nobadays
Member
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# Posted: 20 Jun 2025 10:03pm
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I used LiTime self heating batteries at the cabin all winter to keep Starlink up and running for my WiFi camera. They worked flawlessly! Temperatures hit -19 F and I never noticed my Starlink go down all winter. Now the Lithium Ion batteries in the camera did refuse to charge and ran flat mid winter. They came back up when the Temperatures moderated.
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gcrank1
Member
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# Posted: 20 Jun 2025 11:05pm
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Also keep in mind that if you are not buying 24v LFP bats that not all 12v LFP can be series wired to make 24. I think it is something about the bms's?
I like the idea of having 2 bats that can still run the place on 1 if I gives trouble, thus my 2 100ah LFPs.
Ie, 2 is 1 and 1 is none
Seems Ive also read that you dont want to do 4x 12v LFP wired 2s/2p to make a 24v bank. Best to use 24v bats straight away.
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