| << . 1 . 2 . 3 . |
| Author |
Message |
paulz
Member
|
# Posted: 25 Jul 2026 10:21pm
Reply
Specs for these Humseinks says 10 volt cutoff for BMS. Ive been playing with them since Christmas when they were $100 on sale and my old bank has kept on chugging. One is in my golf cart, one in my old hot rod.
IMG_7482.jpeg
| 
IMG_6878.jpeg
|  | |
|
|
gcrank1
Member
|
# Posted: 26 Jul 2026 08:01am
Reply
If the one you hooked up has shut down when you get back to cabin check it with your voltmeter to see what it is at before you do anything to it; ie, see if it meets the spec, then note that (I use green 'frog tape' notes on my bats with info and hash mark for # of recharges, etc)
|
|
paulz
Member
|
# Posted: 28 Jul 2026 08:16am
Reply
Back at the cabin.. the Wifi died Sunday, meaning the one stand alone LFP did. Got here late Sunday, battery measured half a volt. Jummpered it to the cabin bank, was up in the 11s in minutes. I recall Steve saying that was a typical scenario. Another little while it was up to the cabin bank 13.x.
I thought it might have lasted longer, wifi only draws a couple amps.. It read 13.2 when I started but as Phil said without a shunt i really dont know where in that sweet spot it was. Plan for today is to leave it jumpered to the solar, let it charge all day and repeat the test while here, which will be all week.
|
|
gcrank1
Member
|
# Posted: 28 Jul 2026 09:00am - Edited by: gcrank1
Reply
If you get it charged to where it settles at ~13.3 on a good meter, hook it up and run it until LVD keeping track of the running hours it will me easy to calc the 'amp hours' capacity at that load and can calc the real operating amps draw.
Do you also know when the Wifi died or no? If you do calc those running hours from the 100ah bat rating.
But since you have Plenty of batteries, why not hook 2 parallel, you will have longer run time, wont have a stressing LVD and can recharge them together too.
|
|
paulz
Member
|
# Posted: 28 Jul 2026 10:06am - Edited by: paulz
Reply
Dont know exactly when it died since I have to log into the cameras. Was Ok Sunday morning. I can easily check the amp draw with a dvm while here.
Battery still jumpered to the bank, sitting at 13.15 right now after a night of cabin draw. Sunny day today will bring it up to mid 13s by this evening.
Kind of nice to be able to look at the place from afar. Otoh nice to be able to forget about the cabin while at my old wreck of a house. Only ao much work waiting for us geezers lol.
|
|
philpom
Member
|
# Posted: 28 Jul 2026 10:15am
Reply
For anyone interested, I use this exact shunt in my camper for lithium batteries. Works very well. $37
https://www.amazon.com/BINTA-Voltmeter-Backlight-Waterproof-Motorhome/dp/B0DCN9PRD9/r ef=mp_s_a_1_5?crid=FE3X64Y1Y2CC&dib=eyJ2IjoiMSJ9.PVrssLnrXMO_1RQL6Fa6HXoQ4SDqwPj_vy77 U9INBIGA-w_kqurKfEt-Iynye5oEWNqUdRR2suGqXJ_IivQVdGkjQAFwFVERD2ASCgU2zhXbKrAEfNlEN3Bbi xsNKodSOHHE4_W9rlSJ2MliV5vOgC3fufqKzkYUgSOjdM32T6sYQECc_2dAfxxcsTIwoOtIrYy-oiWrhoFbNH K1SuWX0Q.oOnk9b_iSPxK7p8gsv6xME59BIIo3Qk5Y-dgX42fims&dib_tag=smacab-20&keywords=shunt+batter y+monitor+12v+lithium&qid=1785247957&sprefix=shunt%2Caps%2C220&sr=8-5
|
|
gcrank1
Member
|
# Posted: 28 Jul 2026 11:33am
Reply
That looks like a bit of fun for under $40 
Wife and I can spend that much now on a decent (Not high-roller) meal locally.......
|
|
philpom
Member
|
# Posted: 4 Aug 2026 06:00pm
Reply
It's excellent to have, I've got it wired up so 100% of energy used flows through and every method of charging also flows through, solar or charger. It can display input or output as a percentage or in amps. Works like a gas Guage for the battery. You do need to calibrate it when you first install so it knows your battery bank capacity. It also indicates on the display if you are charging or discharging and I have tested charging while discharging at the same time, handles that fine.
|
|
|
paulz
Member
|
# Posted: 5 Aug 2026 09:10pm
Reply
Put one in my cart. The 150 amp, cant see that I need the 500 amp.. only a buck more…
|
|
philpom
Member
|
# Posted: 6 Aug 2026 09:18pm
Reply
Quoting: paulz Put one in my cart. The 150 amp, cant see that I need the 500 amp.. only a buck more…
Yeah, I believe I installed the 300 Amp version but yes all about the same price. I think you'll enjoy the utility, especially compared to similar far more expensive brands.
This is what I did with mine, tongue box on a tiny camper I built serves as the battery box. I know it's messy but there is order in there it wires to the negative.
20260806_200648.jpg
| 
20260806_200813.jpg
| 
20260806_200840.jpg
| |
|
|
gcrank1
Member
|
# Posted: 7 Aug 2026 10:08am
Reply
I feel myself being slowllyyy sucked in......
lol
|
|
paulz
Member
|
# Posted: 7 Aug 2026 10:19am
Reply
Mine arrives today, stay tuned. Earlier I mentioned my wifi, which I have been running on spare Lfps, on the hopes I can run the cameras while away so I don't risk the cabin bank. I have several, and despite showing adequate voltage last between 1-4 days each. It will be interesting to see what the new meter says.
|
|
philpom
Member
|
# Posted: 7 Aug 2026 01:37pm
Reply
I'm curious too, my guess is either the wifi is pulling a lot of juice or you aren't getting rated capacity out of the battery. If it's pulling 1amp and it's a 100 ah battery then you should be getting about 100 hours run time or pretty close so 4 days sound about right.
Curious how you set up the test. The shunt display is powered by the battery so of course if the battery shuts off there will be no display to read. Ultra low draw and the backlight has auto shutoff.
|
|
paulz
Member
|
# Posted: 7 Aug 2026 02:36pm
Reply
I did get about 4 days out of one bat. The other 2 were only 1-2 days. These were just jumpered to the cabin bank at one time or another, which hits low to mid 13s off the solar. I can charge to 14s with a genny if need be.
Amazon does a day and evening delivery here. Not out for delivery yet so evening could be.
|
|
gcrank1
Member
|
# Posted: 7 Aug 2026 03:04pm - Edited by: gcrank1
Reply
Those bats you are using may each need to be run down to LVD then Fully charged with a 'balancing voltage' (that may be an unknown) of maybe 14.2v.
I know my 12v 100ah bats needed a couple of real use cycles (my short cycles were incomplete) to get them to really saturate? and give me full performance.
They will settle to 13.3ish after a fully charge anyway but there will be waayyy more ah's usable in em.
Now I can recharge to just 13.8 - 14.0 and get Great performance.
|
|
philpom
Member
|
# Posted: 7 Aug 2026 05:59pm - Edited by: philpom
Reply
Just grabbed a new dedicated charger for my battery. I had a portable charger strapped in the box but the display went out. This one should work well. Pretty sure they have it in 20 and 40 Amp variety. Fully automatic, about $50.
Just gotta figure out how to mount it.
Well, no pics, 403 error access to this resource denied
|
|
paulz
Member
|
# Posted: 7 Aug 2026 07:47pm - Edited by: paulz
Reply
Ok shunt installed for testing. 6 amps for spot light, thats all I know so far just clipping it on. The back page of the instructions describes all the reading options. Have to cook dinner, all for today..
Edit: Reading instructions I have to set State pf Charge to 100%, meaning I need a full battery to do so. So I will charge one at 14.2v, see where that holds and set to 100%, I’m thinking. Do I have to do that every time I disconnect or switch batteries?
|
|
philpom
Member
|
# Posted: 8 Aug 2026 12:57pm
Reply
Hmmm. I've only used it for a single battery and only had to calibrate it once but if you move it between batteries then the state of charge, actual capacity, etc will be different so the Guage won't know the state of that battery and it won't be accurate. The values it has were calculated from use and charging of the other battery.
|
|
paulz
Member
|
# Posted: 8 Aug 2026 01:25pm
Reply
Yeah thats how I see it. So I can charge one battery fully, set the gauge and see how it does on the wifi, while im here for the duration.
I could hook it permanently to the cabin bank, 4 batteries in parallel connected to solar.
|
|
gcrank1
Member
|
# Posted: 8 Aug 2026 01:38pm
Reply
It may be close enough with swap out batteries fully charged?
Unless when you unhook it -0-'s the unit? If so, you could do like we have to with changing a battery in newer cars, hook a little bat pack to the cables before unhooking the battery so the computers dont lose power. Iirc some newer bat chargers have that function and think Ive seen little 9v power cells to plug into the cig lighter (probably with key on). Might be cheap on Amazon but you'd have to wire a cig lighter to the bat cables.
|
|
philpom
Member
|
# Posted: 8 Aug 2026 04:37pm - Edited by: philpom
Reply
If they were the same capacity battery but you would still need to tell it the battery was charged because it was taken off of a depleted battery. It doesn't measure voltage to determine point of charge, you tell it the battery's capacity, say 100ah full. It measure amps out so 50ah out and it tells you the battery is 50% charged. Swap it to a full battery and it'll still read 50% charged. It never read 50ah going back in to the battery. Perfect for monitoring a bank. LiFePO4 batteries have a very flat voltage curve when discharging, an initial drop and then nearly flat to about 80% discharge so by the time you read a significant drop they are nearly depleted.
Also, LiFePO batteries should be charged at 14.6v and do not require a float. The BMS will take care of saturation and balancing the cells.
|
|
paulz
Member
|
# Posted: 8 Aug 2026 04:58pm
Reply
I get that. Well I hooked one battery up to my Meanwell charger (running off the inverter connectef to the cabin bank) set to 14.9v. It rose to 14.2 but flattened out there (bank went from 13.1 to 12.8 when powering the charger). Disconnected everything, battery dropped to 13.7 and hung there. Figuring that was as charged as it was going to get, I set the gauge to 100% and hooked up the wifi. Only reads 1.5 amps, 13.2 volts. We’ll see overnight how far from 100% it goes.
|
|
gcrank1
Member
|
# Posted: 9 Aug 2026 05:23pm
Reply
Iirc the top charge V for LFP is 14.6, though I know we get more amps delivered with the Meanwell per supplies the higher we crank em up. Wouldnt want to space out and leave em at 14.9 too long......
Guru Steve recommends 13.8 as a regular top though Ive upped my MW to 14.2ish which seemed to get my bats over their sluggishness to top up. I DO KEEP my eye on the time and typically recharge the 100ah bat in 2.5hrs now. The bit lower recharge amps at that set V is still sooo much better than lead acid that I dont fret it.
|
|
paulz
Member
|
# Posted: 9 Aug 2026 05:57pm
Reply
Same here. When I have to augment the solar with a genny and MW I keep a close eye out.
Well the Wifi, 100ah bat and shunt meter have been going for about 24 hrs. It reads 70% left. The wifi shows a 1.2 amp draw, so if I started with a full bat I’ll get another 2 days +. One amp on a 100ah bat should be 4 days, so Im getting close..
|
|
philpom
Member
|
# Posted: 9 Aug 2026 06:03pm - Edited by: philpom
Reply
Nice, getting close to the answer. Now I'm curious how 200 watts of solar would stretch the runtime.
Probably indefinitely.
|
|
| << . 1 . 2 . 3 . |
