#153234  by greynz
 Sun Jul 21, 2019 6:09 pm
Just need a few pointers to see if this is gonna work ok, or to find something better.
Have 1200w solar, 6x100ah lead crystals setup as 300ah 24v. Panels are in two pairs & 2x 30A Tracer controllers.

I’ll be needing another charger so either one to run off alternator or more likely the generator (have one anyway which will be running sometimes regardless). I remember when sussing out batteries that lead crystals need high current charging but kinda forgot at the point of ordering...although it seems that it can be just an occasional thing.. The manufacturer specs would suggest for my size bank i’d need 90A charging at 24v.
One option might be to isolate one pair at a time and give a full charge with a 30A charger off the generator. Don’t mind doing that every few weeks or so if necessary. But could the charger off the generator run at the same time as the solar controllers & potentially mean 3x 30A chargers going to the whole bank?

& please don’t say just get lithium :lol:

Thanks
 #153239  by mattn
 Mon Jul 22, 2019 8:16 am
Lead acid batteries (Lead crystals are a version lead acid with a mix of snake oil) require a long time to charge -8-12 hours minimum. While charging of an alternator is useful, its only worth while because its cheap to install. Practically, unless you typically do big miles its a useful top up.

Do not split the banks. Its much better to charge the two banks at half the rate than one bank then the other. The 90A recommendation is a balance between cost and capacity to charge in a reasonable time. When you say 'I'll be needing another charger' - why? Charging slower does not affect the batteries, but in a motorhome you do want to be able to get the charged in a reasoanble time - sizing for charging from flat overnight is about right - 300AH with about about 50-60AMPs would be sufficient (30Amp if dollars are a problem would be adequate, but a full charge from flat will take two nights)

If you are running out of power and want to charge for generator, you want to run the generator at capacity so it runs for the shortest time possible. No matter what you have,m the batteries will still take 8-12 hours to charge. You will however get flat batteries to about 90% charged relatively quickly - 2-3 hours - if you have a large enough generator and charger. In this case I would be suggesting 100 or even 150Amp, but that generator has to be big enough.
 #153240  by greynz
 Mon Jul 22, 2019 10:51 am
Thanks Matt, for general day to day living we won’t use that much so hoping the solar will keep things ticking over ok, but there will be times when working that we’ll have a generator running anyway and also using more from the batteries, so figured it would be good to have a charger hooked up at the same time and just make the most of it.
The 90A charging is from a Betta batteries video about charging lead crystals, something to do with that snake oil needing an occasional high current full charge, so just trying to see if I can do that without too much expense. Supplier suggested isolating the batteries in pairs for individual charging but just not sure if that’s really the best way.
 #153241  by mattn
 Mon Jul 22, 2019 12:35 pm
I would need to see the data sheet for your specific batteries, but Betta won't let me down load them without handing over my first born.

90Amp into 200AH batteries is 0.45C - adding the 30AMP solar input, you are potentially up to 0.6C Splitting the bank and using a smaller 30AMP charger, your still potentially charging at 0.6C. While I have no hands on experience with Lead Crystals, these numbers are incredibly high, one datasheet I have studied talk about charging at around 0.3C, which is significantly higher than typical lead acids (typically recommended rate is 0.2C).

A 90Amp charger delivering 28.8V, into a wall socket, its drawing over 10AMPs, make a coffee with the Nespresso and you pole breaker will pop. Its also sucking a lot of gogo juice out of a generator, if used for other things, may be too much.

I would probably go with 40-50AMP charger. That needs about 1.5kW out of the generator and will take a half day to 'mostly' charge even excessively flat batteries. If plugged into mains, you can still make a coffee. If you are using the genny for other stuff, you need to be mindful of not overloading it.
 #153242  by greynz
 Mon Jul 22, 2019 12:57 pm
Thanks Matt, appreciate it, i don't really have the technical skills to talk knowingly if that makes sense! The charging specs do state the 0.3c you mention.

The 90A would be for the 300ah bank, I'll have 2x 30 amp solar controllers & was hoping a seperate 30A charger would work to give an occasional full 90A charge altogether?
 #153245  by mattn
 Mon Jul 22, 2019 3:01 pm
Sorry - got it into my head that it was 200AH of battery.

From what I see Lead Crystals must be charged at 0.3C. That must word gets bandied around quite often. To me, it is synonymous with "not suitable for solar installations" . Problem with solar is you cannot rely on it to supply consist current, so to get the required C0.3, you need a 90Amp charger or need to split your battery banks, with the complexity and hassle of managing them that is far from ideal).

Solar is great for charging batteries like AGM and Lithium, as these technologies do not have a minimum charge rate.
 #153246  by greynz
 Mon Jul 22, 2019 3:23 pm
Yeah i’m a bit concerned.. although the Betta guys have a video on YouTube about charging, which kinda says that you can go for weeks/months away relying on usual solar setups as when you get back they get a full charge at 0.3. So pretty much every once in awhile...I guess I need to nail down with them really how often that has to be.
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