Electrical/Battery issue.

[msmith1199]

Question about electrical issue.
I have two 100 watt LiPo batteries. Been dry camping for 7 days now. The first 3 were on the road so batteries were charged by alternator for the first three and the generator only for the last 4. Everything has been going fine until last night. I turned the generator off at 10pm and it had run at least 5 hours during the day, maybe more. But at 1am my batteries died. I knew they died because my CPAP tried to suffocate me! :).

I have a residential fridge and my Satelite receiver was on, but other than those and CPAP there wasn’t much other electrical draw. So the only thing I can conclude is for some reason the batteries didn’t fully charge. They are charging today and I can get power out of the inverter so I know the charger is working.

I’m not much of an electrical guy but I check the voltage at the converter with the generator running and it’s at 14.5 volts. The voltage at the batteries both with the generator running and without is 13.6 volts. I think those numbers mean it’s should be working fine.

The only thing I did different yesterday over any of the other days is whenever I had the generator running I had the A/C on. Is it possible all the power was taken by the A/C and wasn’t going to the converter to charge the batteries? That’s the only thing I did different yesterday over the others.

[3_tons]

You didn’t say how you are determining state of charge…Determining SOC with lithium (LiFePo4) batteries can sometimes be problematic due to what is an uber flat voltage discharge curve, and I would think that running a CPAC is mission critical…Do you have a lithium capable SOC (state of charge) meter such as a Victron Smart shunt, or a BMV-12 or equivalent?? …If not, then it’s gonna be difficult for you to know what your true SOC is - voltage alone may not be telling you the whole story…

Outside of that, when your battery is undergoing a charge, you’ll need to see a voltage at the terminals of somewhere around 14.2 to 14.6 v and holding to achieve a full charge, yet this will occur prior to a passive internal cell-balancing regime which can usually take (depending on number of less than full charge battery cycling) say another 15-30 min or so - this phase can be readily monitored on your SOC meter via intermittent amps vs volts until holding at near zero amps (assuming no load)…After this, it is best to discontinue longer term charging to avoid the possibility of dreaded dendrite formation that may occur due to such overcharging…

3 tons

[theoldwizard1]

msmith1199 wrote:

I have two 100 watt LiPo batteries.

I assume you mean 100 Amp-hour (Ah) batteries. I also assume you have LiFePO4 batteries)

msmith1199 wrote:

Been dry camping for 7 days now. The first 3 were on the road so batteries were charged by (vehicle) alternator for the first three and the generator only for the last 4.

The power source is not the issue. What are you using for charging ?

Hooking directly to your tow vehicle 12VDC is NOT the best way to charge yoiur batteries. You will never get 100% fully charge that way. You really should be using a DC-DC charger with output settings for LiFePO4

Second, a "standard" converter is NOT the best way to charge your Li batteries either. You will never get 100% fully charge that way. Get a converter that is designed to charge Li batteries.

Better yet, remove the converter and your current inverter. Replace them with a combination charger/inverter/automatic transfer switch. Wire your 12VDC circuit directly (via a fuse) to the battery bank

[wolfe10]

msmith1199 wrote:
The converter is putting out the 14.5. The 13.6 is at the battery.... So I don’t know if it’s supposed to show 14.5 at the battery when charging or if it’s correct in showing 13.6 even when charging.

The only reason for a higher voltage reading at the converter than at the battery bank is RESISTANCE between the two. Could be a connection at one end or the other, could be a fuse (if there is one) between them, could be too small a gauge wire.

And, the lower the charge rate, the less voltage drop you should see.

[msmith1199]

Okay, batteries lasted all night and showed fully charged still this morning. I ran the generator longer yesterday and reduced power consumption so I don’t know which one really fixed the problem. But the problem is solved. I’ll just keep that pattern going.

[wa8yxm]

What is the make and model (And ampreage) of your converter

You have 300 amp hours of batteries. Let's say you use 80% (240 amp ours)

Well converters can be as low as around 20-25 amps or as high as 100.
To replace 240 amp ours will take at least 250 amp hours.. 25 amps that's 10 hours in theory.. but wait there's more.

As the battery charges the converter "Backs down" a bit so it might take 12 or more.. and if it's not a LI-charger (Still an LA charger (Lead acid) it may well never it 100% because it simply has not the push to do it.
3.4 volts resting. 3.65 charging times 4 cells = 13.6 volts resting and 14.6 charging.... Many converters are 13.6 Float(that's good) and some that's all they do and 14.2-14.5 Boost/Absorption (Not enough) to fully charge LiFePO4.
(Voltage source google)

[msmith1199]

ScottG wrote:
From your orig post "The voltage at the batteries both with the generator running and without is 13.6 volts. I think those numbers mean it’s should be working fine."
13.6 is not going to charge Lithium batteries. Something is very wrong between the converter/charger and your batteries. You should be seeing well over 14V.

The converter is putting out the 14.5. The 13.6 is at the battery. According to sources I looked up, 13.6 indicates a fully charge LiPo battery. So I don’t know if it’s supposed to show 14.5 at the battery when charging or if it’s correct in showing 13.6 even when charging.

[msmith1199]

CA Traveler wrote:
OP Your posts suggest that over the 7 days you used 160AH (80%) of your batteries that was not replenished due to inadequate charging. It's likely setup for flooded batteries and not for the LiPo batteries.

Your A/C is not the cause. If your A/C plus charger tried to draw more AC amps that the CB rating then the CB would have tripped on the gen.

It’s set for LiPo

[ScottG]

From your orig post "The voltage at the batteries both with the generator running and without is 13.6 volts. I think those numbers mean it’s should be working fine."
13.6 is not going to charge Lithium batteries. Something is very wrong between the converter/charger and your batteries. You should be seeing well over 14V.

[pianotuna]

The OP is seeing 14.5 volts when the generator is running.

I wonder why the batteries are not fully charging when presented with that?

[CA_Traveler]

OP Your posts suggest that over the 7 days you used 160AH (80%) of your batteries that was not replenished due to inadequate charging. It's likely setup for flooded batteries and not for the LiPo batteries.

Your A/C is not the cause. If your A/C plus charger tried to draw more AC amps that the CB rating then the CB would have tripped on the gen.

[msmith1199]

Yes, I meant AMP. Told you I’m no electrician! And it’s only one A/C. I’m guessing I wasn’t at full charge, but I don’t understand exactly why. Like I said, I’m on day 7 and every other day there was power in the batteries to last all night. And when starting the generator the next morning you can tell the batteries were still strong. Just wondering why on night 7 it didn’t work. The tech department at the converter maker said it’s possible I was simply using 5% a day more power than I was charging and by the 7th day that resulted in a 35% loss so that’s why it gave out on the 7th day. I’ll run the generator longer today and see what happens tonight.

[wa8yxm]

First you said "100 watt" that's about 10 Amp hour

Or did you mean 100 amp hour.. Ok.
Item 1: Unless you upgraded the conveter to an LI they never hit full so you don't have the full 200 AH (I'm assuming 200 ah total) You might have 180-190 but even to get there takes 6-8 hours of generator time or more depending on your converter.

Next that Refrigerator is likely around 200 watts running 100-150 average. Divide by 10 or 12 volt power consumption so it's 10-15 amps.. You only have woo
The sat receiver may well draw as 30-70 100 watts (3-10 amps)
We are now up to around 25 amps draw You only have 200 amp hours and I've not yet added in the CPAP (those can draw a bit of power if humidified. and that's the best kind) so you are below 8 hours at full charge.. and you were not likely at full charge.

[rjstractor]

MNRon wrote:
Does AC mean one or two 15kW ACs? If two, most likely that sucked up most of the power the genny could provide and starved the battery recharge. I don’t know what converter you have, but if standard it probably can’t provide more that ~50A per hour to the batteries (or less); that would require 4hours of charging for two fully depleted 100AHr batteries.

Unless the generator has some kind of sophisticated load shedding feature that prioritizes some circuits over others, I don't think this is how it works- if the generator were overloaded it should trip its main breaker. (I'm assuming you meant 15K btu, not 15kW)

[CA_Traveler]

Plus LiPo batteries have a unique charging profile and at best take a long time to charge with the common flooded charger. Plus your alternator and long wires likely did almost no charging while driving.

So are you setup for LiPo charging or did you just do a battery swap? Also a battery monitor will enable you to know the battery charge state.