Originally Posted by Bud
"There are always lots of discussions as to the usefulness, or not, of solar on a B van, but sometimes it works out very well for us."
So please take a guess at just how well it worked.
With a cold engine and house batteries down 50-60%, how many minutes/seconds would it have taken to produce the same result as your solar with the 6.0?
Hi Bud, this one may surprise you, or not. The critical part is your requirement to have the batteries at 50-60% at the start of the charging.
We were using in the 50-60ah per day, I think, so with the engine generator we could replace that with about 20 minutes of engine running, IF THE BATTERIES WOULD ACCEPT FULL OUTPUT.
The problem is that when the batteries are at about only 10-15% down like we were, the batteries are way into the tapering stage of the charge and won't accept many amps. I would guess if we are 10% (44ah) down, the batteries would accept mabey 15 amps after the first couple of minutes, and it would taper from there.
In our case, solar covered use, and charged batteries, during the day, and then we used battery power overnight, typically being 15-25ah down by morning. It would take the solar about 3-5 hours to top off the batteries to the point they were accepting only 2 amps. The solar was not maxed out unless we were running something that pulled over 10 amps in most cases.
My guess would be that starting at 50-60ah down, with the long top off time needed with lead acid batteries, you would be looking at upwards of 4-6 hours minimum of engine running, the same as the solar took plus a bit more for the larger recovery needed.
If our batteries were down in the 50% state of charge range, we would be able to get that 50-60ah recovery in 20 minutes or so if driving and about 30 minutes idling, as the batteries would accept the amps if they are that far down.
While I certainly am not afraid to run the batteries in the middle of the SOC range for around 5-10 charge cycles before a good full charge, it is always better for the batteries to operate in the top end of the SOC range.
IMO this is the prime advantage and usefulness of the solar, as it can finish the charging cycle to 100% full without having to drive that extra 4-5 hours or plug in. If we were at 50% SOC, I would turn on the engine generator until the batteries were accepting about 10-12 amps, and then let the solar finish it with or without driving. That leaves you at about 1-1.5 hours of driving and 4-5 hours of solar to get your periodic full charge. Without the solar, you have to either drive the 4-5 hours or find shore power to get the periodic full charge taken care of. From 50% we would be looking at 220ah recovered, so it would be a fairly large recharge cycle.
This way, even a small amount of driving, plus decent sun, can totally free us from shore power or long periods of driving, while still taking very good care of the batteries by getting full regularly.
Of course lithium batteries are totally different and will operate forever in the middle of the SOC range without issue, and will accept the amps, so all this doesn't apply to them.
Bottom line is that, for us, the solar eliminates, almost completely, the main weakness of the lead acid batteries, which is the need to go through the very long time on charge needed to get them to 100% every 5-10 charge cycles. Of course, the solar is also quite a bit quieter and less disturbing to us and others than running the van engine