โApr-06-2021 06:25 PM
โApr-21-2021 07:02 AM
BFL13 wrote:
I would never trust the %SOC of a monitor. I do trust the AH count. I don't have the Trimetric set-up to even read %SOC. I do have an idea of the battery bank's AH size as adjusted for temperature. This matters when camping in ambient 35F temps.
I look at the AH countdown from zero and subtract that in my head from my notion of battery bank size in AH to get an idea of SOC. I know my daily usage. Easy to tell if I need to recharge today or if it can wait till tomorrow.
I have the voltage read-out too. I mostly watch that for estimating SOC, which is also easy with "ordinary" batteries. I cross-check the two SOCs to see if they "match". No big deal, no spoiling of quality camping time.
It is easier in the summer with solar, where you can go for weeks without getting down to where you need to haul out the gen. Do have to keep an eye on the weather forecast for overcast predictions. I do watch for when the batts get to "true full" while on solar, and reset the AH counter. If it doesn't get to true full that day, I just leave the AH counter running. ( I have disabled the auto-reset on the Trimetric like they suggest if you are on solar)
If I had LFPs I would not change my ways, except I would miss having the more "accurate" voltage readings.
โApr-21-2021 06:58 AM
time2roll wrote:
If the battery is cold and loses 30% of the capacity does the counting of AH still add up? If you know the battery is cold the voltage will still be dropping quick in the last 30%.
What ever system you have is but a guide. Keep your wits about you and all will be fine.
โApr-21-2021 05:04 AM
โApr-20-2021 10:18 AM
โApr-20-2021 09:34 AM
FWC wrote:If the battery is cold and loses 30% of the capacity does the counting of AH still add up? If you know the battery is cold the voltage will still be dropping quick in the last 30%.
Coulomb counters/Ah meters work very well (when configured properly), and can easily track the battery SOC to 10% or so, which is plenty accurate for RV use. I am not sure why this is causing so much concern.
If you know the temperature of your LiFePO4 batteries, and the loads, you can probably get an estimate within 20% - 40% using voltage, but it is much more complicated than just glancing at your Ah meter.
I know folks like to fuss over their power systems (it is a hobby unto itself), but the point of a well configured system is the you don't need to be constantly thinking about it, it just does it't thing in the background. If you are running a decent size battery system of any chemistry, and Ah meter seems like a no-brainer, you can glance at it every once in while to make sure everything is OK, no need for tables, maths etc.
โApr-20-2021 09:24 AM
BFL13 wrote:
FWC has shown how temperature changes the LFP voltage so much that you can't really use the voltage/SOC table if I understand him on that. I don't know if you can use a temp/voltage table and allow for the temp so you get "close enough".
The main thing you want to know while camping is whether you need to haul out the gen today or can it wait till tomorrow to do a recharge. You need your SOC now to decide that based on your planned usage between now and tomorrow. Solar is part of that decision of course.
"Close enough" is where the accuracy of the voltage reading matters. An AH counting monitor would be a better guide IMO, with your estimated adjusted for temp, low load, "resting" voltage as a rough cross-check.
โApr-20-2021 09:04 AM
โApr-20-2021 08:44 AM
โApr-20-2021 08:41 AM
StirCrazy wrote:pianotuna wrote:
Why not just write the seller/maker?
Who is the most 'senior' user of Li here? (i.e. longest use)
I have had a cell phone for 30 years ๐
probably not me, I have been playing with small 30AH batteries for about 2 years now but thats it.
Steve
โApr-20-2021 08:18 AM
hold up therebig guy, yes you can use voltage in 10% aproximations
โApr-20-2021 05:28 AM
pianotuna wrote:
Why not just write the seller/maker?
Who is the most 'senior' user of Li here? (i.e. longest use)
โApr-20-2021 05:25 AM
BFL13 wrote:
With LFPs it seems you can't believe the Wh or the AH ratings to use with your monitor and you can't really match the voltage with the AH count to do cross checks.
Apparently all you have is your AH counter to go by. So my new plan is to use your "allowance" (as described earlier) and use that as your "capacity" never mind what the real capacity might be in the strange LFP wonder-world of inconsistent numbers. YMMV (and no doubt does! ๐ )
โApr-19-2021 02:36 PM
time2roll wrote:
I read some inverters have 2 stage charging. Bulk, absorption and off. At the set point, 12 to 13 volts, the charger repeats the 2 stage.
โApr-19-2021 02:00 PM