Bad Converter Charger
Wife & I are out in Truck Camper. Usually take a look at an app on my phone that links to my solar charge controller. It showed the batteries at 16.78v WOW! I have a multimeter & got to diggin...
Forum Discussion
"....their 15a version as my 2 batteries have a 30a max 60a total charge limit. I will be getting about 45a through solar on the sunny days & when running the generator or shore it will kick on the 15a charger=60Amps total I don't want to fry these batteries they aren't cheap. "
AGMs do need special attention and a set-up for doing that.
1. They require a 20% charging rate when you can arrange that at least every few cycles. They have a max charging limit of about 30%.
2. You can only get them to accept 20% when they are under about 75% SOC or above that SOC they will go straight to the Absorption Stage with tapering amps with those amps being under the 20% desired.
You are concerned the 45amps of solar plus whatever the converter does will add to more than the 30% limit.
220AH of AGMs in sig, but above quote implies 200AH , so using 200, 20% is 40amps, and 30% is 60 amps as in the above quote.
You need at least a 40 amp converter for when there is no sunshine, and the solar will only meet the 20% spec on a sunny mid-day period for a short time before amps drop as the sun gets lower.
You need to get the batts down under 75% to meet the 20% at all, and to get any time in Bulk at 20% you need the batts even lower in SOC at the start of the recharge.
I had this problem, and when leaving the campground for home with the batts nicely down below 75%, the drive home with alternator charging plus solar got them above 75%. So at home I did the recharge on shore power, but was not meeting the AGM 20% spec, only the 0.5a/100AH spec. What to do?
Before leaving the campground I disconnected solar and alternator charging so the batts stayed low. That means you need a way to do that. Solar is easy since you should already have a switch method between array and controller so you can disconnect the array before disconnecting the battery and VV as required by some controllers--Morningstars eg.
Alternator charging disconnect depends on the rig. Pull the 7-pin or put in a switch on the line to the house batts if a MH.
Now what about the other problem of going over 30% when on solar and converter and they are adding their amps? First, the battery has its own acceptance rate limiting where it will accept more amps at a lower SOC and at a higher voltage. Your voltage needs to be 14.4ish to meet the AGM spec, so that is fixed--set that for the controller and your adjustable converter you are getting. They will add their amps having the same set voltage.
If your converter will do at least the 20%, just use that and shut off the solar until amps taper well down, then shut off the converter.
You could get a 55 or 60 amper and be ok as long as you have a 2000w gen or bigger. (A 1000w gen will only run a 40 amper at 14.4v or about that.)
And you do need the ammeter to see when you are down to 0.5a/100AH, but usually only at home, since you won't run the gen that long while camping--maybe doing 50-90s-- or on solar you will be doing more like 75-95s and never get them that full either. A Trimetric or similar monitor with shunt will do the ammeter job. (not the solar display which also shows the amps to loads--a monitor shows only battery)
BTW that is how solar kills batteries! Doing shallow cycles that never quite get the batts full, so they sulphate sooner than they would normally. You have to break that pattern and do a proper deep cycle to true full every so often, even if it is a PITA to organize.
AGMs do need special attention and a set-up for doing that.
1. They require a 20% charging rate when you can arrange that at least every few cycles. They have a max charging limit of about 30%.
2. You can only get them to accept 20% when they are under about 75% SOC or above that SOC they will go straight to the Absorption Stage with tapering amps with those amps being under the 20% desired.
You are concerned the 45amps of solar plus whatever the converter does will add to more than the 30% limit.
220AH of AGMs in sig, but above quote implies 200AH , so using 200, 20% is 40amps, and 30% is 60 amps as in the above quote.
You need at least a 40 amp converter for when there is no sunshine, and the solar will only meet the 20% spec on a sunny mid-day period for a short time before amps drop as the sun gets lower.
You need to get the batts down under 75% to meet the 20% at all, and to get any time in Bulk at 20% you need the batts even lower in SOC at the start of the recharge.
I had this problem, and when leaving the campground for home with the batts nicely down below 75%, the drive home with alternator charging plus solar got them above 75%. So at home I did the recharge on shore power, but was not meeting the AGM 20% spec, only the 0.5a/100AH spec. What to do?
Before leaving the campground I disconnected solar and alternator charging so the batts stayed low. That means you need a way to do that. Solar is easy since you should already have a switch method between array and controller so you can disconnect the array before disconnecting the battery and VV as required by some controllers--Morningstars eg.
Alternator charging disconnect depends on the rig. Pull the 7-pin or put in a switch on the line to the house batts if a MH.
Now what about the other problem of going over 30% when on solar and converter and they are adding their amps? First, the battery has its own acceptance rate limiting where it will accept more amps at a lower SOC and at a higher voltage. Your voltage needs to be 14.4ish to meet the AGM spec, so that is fixed--set that for the controller and your adjustable converter you are getting. They will add their amps having the same set voltage.
If your converter will do at least the 20%, just use that and shut off the solar until amps taper well down, then shut off the converter.
You could get a 55 or 60 amper and be ok as long as you have a 2000w gen or bigger. (A 1000w gen will only run a 40 amper at 14.4v or about that.)
And you do need the ammeter to see when you are down to 0.5a/100AH, but usually only at home, since you won't run the gen that long while camping--maybe doing 50-90s-- or on solar you will be doing more like 75-95s and never get them that full either. A Trimetric or similar monitor with shunt will do the ammeter job. (not the solar display which also shows the amps to loads--a monitor shows only battery)
BTW that is how solar kills batteries! Doing shallow cycles that never quite get the batts full, so they sulphate sooner than they would normally. You have to break that pattern and do a proper deep cycle to true full every so often, even if it is a PITA to organize.
