Victron Energy: Alternator/Solar Charging - LFP Battery System

[shade]

Why is the 100A fuse an issue relative to an alternator?
I see the next post indicates a 100A fuse could handle 130A over time.
So if that 100A fuse gives 80A thru the BMS 12/200, is that not a good charge current for 100Ah or 150Ah LFP?

80A is plenty for a 160Ah LFP battery; a little too much, actually. My alternator probably wouldn't be able to maintain that for too long, but the battery capacity is fairly small.

I may still end up with a 12/200. I'm just waiting to see what's what when Victron announces new DC-DC chargers in November.

My quest to buy a single +300W panel may put off fixed solar charging until I can pick up a panel in November. No retailers are close to me, and shipping is high. I can make do with a 100W panel I already have, but that's not ideal. AFAIK, the 160Ah battery will ship soon. We'll see.

 

[shade]

Another delay for mounting a panel is the overdue delivery of a Kinsmen Awning I ordered months ago. I'm not quite ready to start bad mouthing the company, but I'm getting close. I need to mount the awning before I can make a mount for a solar panel, so it'd be swell if it was delivered only two months late.

 

[dreadlocks]

Loosing an alternator because you over worked it would be a bad way to get stuck in BFE.. mebe if the sun is strong enough you can make it back

I'd rock it w/solar right now too.. just put those manual over-rides on the battery protects in so you can just drop all loads and let solar do its thing uninterupted.

As long as I'm not parked right under a treee, my 325W hit w/100AH LFP has been more than adequate.. even on some overcast days its easy enough to cover the fridge load and get the battery high enough by end of the day that its got no problem getting through the night.. It taking full charge rate pretty much any time is really damn nice.

 

[shade]

Loosing an alternator because you over worked it would be a bad way to get stuck in BFE.. mebe if the sun is strong enough you can make it back

I'd rock it w/solar right now too.. just put those manual over-rides on the battery protects in so you can just drop all loads and let solar do its thing uninterupted.

As long as I'm not parked right under a treee, my 325W hit w/100AH LFP has been more than adequate.. even on some overcast days its easy enough to cover the fridge load and get the battery high enough by end of the day that its got no problem getting through the night.. It taking full charge rate pretty much any time is really damn nice.

Yeah, I don't see myself pushing my 130A alternator for more than 50A, and that shouldn't be for more than a few hours at most with a 160Ah battery. That would keep alternator charging in the 0.3C range, so good for the alt & battery. I'll still check alt temps no matter what to see how it fares at whatever the maximum output ends up being.

On solar charging, is that your experience with one or two 325W panels?

 

[dreadlocks]

Just the one, I went most of the season leaving the 2nd panel behind.. I took it out once when I thought I'd need it due to it being a deep, narrow valley and nice thick healthy forest.. I needed it, but then again my LFP crapped out that weekend so mebe I didnt..

 

[shade]

Just the one, I went most of the season leaving the 2nd panel behind.. I took it out once when I thought I'd need it due to it being a deep, narrow valley and nice thick healthy forest.. I needed it, but then again my LFP crapped out that weekend so mebe I didnt..

Oh, that's great! - Well, not the BB taking a dump part.

I thought you were usually running both panels for charging. If just one is working that well for you, I may rarely use alternator charging.

 

[SBDuller]

I'm not suggesting to overwork the alternator, really have no idea how close to overworking it currently is when charging two AGM's. I have not heard any rumblings of Alternator distruction from the dual battery crowd. I understand that having as much PV area as possible is better, but my reality is 200W rating max, and that makes me wonder is it better to stay with 100Ah, or reach for 150Ah.

 

[shade]

I'm not suggesting to overwork the alternator, really have no idea how close to overworking it currently is when charging two AGM's. I have not heard any rumblings of Alternator distruction from the dual battery crowd. I understand that having as much PV area as possible is better, but my reality is 200W rating max, and that makes me wonder is it better to stay with 100Ah, or reach for 150Ah.

LFP batteries are a different animal, and they can suck down much higher rates of charge than Lead Acid. Most dual battery setups seen are using some form of LA batteries (like those AGMs), which don't tax an alternator unless it's a high capacity bank bulk charging.

 

[Alloy]

Why is the 100A fuse an issue relative to an alternator?
I see the next post indicates a 100A fuse could handle 130A over time.
So if that 100A fuse gives 80A thru the BMS 12/200, is that not a good charge current for 100Ah or 150Ah LFP?

If the alternator is trying to push 130A and the battery is accepting 130A then a 100A fuse between both will either blow or generate heat. Heat degrades fuses.

100Ah Lithium will accept 100A without damage
150Ah Lithium will accept 150A without damage


-Charging
80A is 1h to full (20-100%) charge with 100Ah
130A will degrade a 100Ah battery.

80A is 1 1/2 hours to full charge with 150Ah
130A is 1h9m to full charge with 150Ah

 

[shade]

If the alternator is trying to push 130A and the battery is accepting 130A then a 100A fuse between both will either blow or generate heat. Heat degrades fuses.

100Ah Lithium will accept 100A without damage
150Ah Lithium will accept 150A without damage


-Charging
80A is 1h to full (20-100%) charge with 100Ah
130A will degrade a 100Ah battery.

80A is 1 1/2 hours to full charge with 150Ah
130A is 1h9m to full charge with 150Ah

If we're still talking about using the Victron 12/200 BMS, the fuse in the BMS is used to regulate the load on the alternator.

While they can accept much higher charge rates, the recommended charge current for Victron LFPs is 0.5C or less.

 

[Alloy]

If we're still talking about using the Victron 12/200 BMS, the fuse in the BMS is used to regulate the load on the alternator.

While they can accept much higher charge rates, the recommended charge current for Victron LFPs is 0.5C or less.

If the alternator is 130A or 200A the Victron 12/200 with a 100A fuse will regulate the charge to the (not the FLA) Lithium to 80A?

Good to know about the 0.5C. Looks like BB is the same but that's "marginally" better than my FLA.

 

[luthj]

Peak charge and continuous charge are very different. FLA will taper rapidly, while Lithium will accept sustained charging at 0.5C from zero all the way to the 90% SOC range.

The alternators "rating" only has a passing relation to the charge rate. Charge rates are always less than the alternators rating, almost always under 70% for factory sized alternators. My 500AH AGM bank has never pulled more than 130A from my 200A alternator.

 

[shade]

If the alternator is 130A or 200A the Victron 12/200 with a 100A fuse will regulate the charge to the (not the FLA) Lithium to 80A?

Good to know about the 0.5C. Looks like BB is the same but that's "marginally" better than my FLA.

From the 12/200 datasheet:

5. The input current is electronically limited to approximately 80% of the AB fuse rating. A 50A fuse, for example, will therefore limit the input current to 40A. Choosing the right fuse will therefore:

a. Protect the LFP battery against excessive charge current (important in case of a low capacity LFP battery).

b. Protect the alternator against overload in case of a high capacity LFP battery bank (most 12V alternators will overheat and fail if running at maximum output during more than 15 minutes).

c. Limit charge current in order not to exceed the current handling capability of the wiring. The maximum fuse rating is 100A (limiting charge current to approximately 80A).

 

[shade]

I'm trying to find out more about this tidbit from the BMS 12/200 datasheet:

"3. Excessive input voltage and transients are regulated down to a safe level."

I already know it allows regulation of charge current, and it isolates the start & house batteries. If it offers sufficient overvoltage protection, I might just go with it and move on.

 

[dreadlocks]

yeah both panels full in sun is totally overkill for me, ******** it can run more than half the microwave off the frigging sun haha.. when I mount the second one to the side of the trailer and make it portable it'll be even easier.. only when the fixed is in a tough spot or if I want comfortable outputs in overcast would I need to take the portable one off the side..

I figure that might change tho if I get an eBike or something with its own sizable lithium battery that wants to charge at several hundred watts.. then I might find my self dragging the portable one out into the sun even if the fixed panel is doing fine.