connecting a smart charger to panel input on solar charge controller?
Submitted: Sunday, Apr 28, 2013 at 10:06
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kcandco
Hi
I am camping with my brother who has a 80w solar panel charging van battery through a cmp solar regulator. He also has a ctec 15amp 8 stage smart charger. The regulator keeps a reading of the total cumulative charge to the battery and cumulative load on the battery. If he connects the charger straight to the battery, it will bypass the regulator and thus the cumulative charge readings will be incorrect. Is it possible to connect the smart charger using the solar input to the regulator. This would mean the readings for the cumulative charge would still be correct. My thoughts are that connecting the charger in normal mode may cause problems due to voltage readings, but wonder if connecting in power supply mode would be appropriate.
I would be interested to hear if someone is doing this, or if it is safe/appropriate to do so.
Thanks Kc
Reply By: Member - John and Val - Sunday, Apr 28, 2013 at 14:36
Sunday, Apr 28, 2013 at 14:36
kc - Sorry, won't work. The controller won't accept the charger and the panels simultaneously. The charger won't like the higher panel voltage being applied to its output and may be damaged by it. With the panels disconnected, the controller is designed to manage the panel voltage and will not manage the lower charger voltage. So No - don't do it!
One other point - don't take too much notice of the cumulative charge readings. Batteries aren't 100% efficient so a simple calculation of input - output doesn't give a net charge figure. In fact the controllers assume a certain efficiency and calculate that in - BUT - effiiciency varies quite a bit with temperature, age of battery and the size of charge/discharge currents, so the net figure is pretty rough. A good indicator, but a poor measurement.
Cheers
John | J and V
"Not everything that can be counted counts, and not everything that counts can be counted."
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Follow Up By: Member - John and Val - Sunday, Apr 28, 2013 at 15:38
Sunday, Apr 28, 2013 at 15:38
Just to clarify - my wording above is horrible! - the solar controller is expecting to see solar panels capable of an output voltage up to 20+ volts. The charger won't deliver more than about 14.5 - 15V, so the solar controller won't know what to do with it.
The smart charger won't know what it's about either if it isn't connected directly to the battery. Overall, not a good idea!
Cheers
John | J and V
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Follow Up By: Member - graeme W (WA) - Sunday, Apr 28, 2013 at 22:35
Sunday, Apr 28, 2013 at 22:35
Hi
John and Val. This may be slightly different and if you read the post i put up today on solar
test you will see my setup. When we are camped in shade with not enough sun for the panels to work and when at
exmouth every year insread of running my fridges on 240 volts i just leave my xantrax 40 amp smart charger hooked up to an anderson plug connectected to my back battery (used mainly to connect the van battery for charging when travelling) and either run the gennie or 240 if availible to keep the batteries charged to run the fridges. My solar regulator simply cuts out when it sees the high voltage from the xantrax thinking every thing is charged. Been doing this for 7 years now.
Cheers Graeme
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Follow Up By: Member - John and Val - Monday, Apr 29, 2013 at 08:30
Monday, Apr 29, 2013 at 08:30
Hi Graeme,
Yes - good way to go. Our own system relies entirely on 12V, maintained using a 240V charger if mains power is available when sunlight isn't. Keeping the solar charging and 240V charging independent from each other as you (and I) do is fine. The only interaction is, as you say, that the solar controller sees the charging voltage from the mains charger and concludes that the battery is now full. No problem.
However, the original poster was considering hooking his 240V charger into the SOLAR INPUT of his controller so that the controller could monitor net in/out current flow. Nice idea, but with insurmountable problems! Far better to simply connect the OUTPUTS of both charging sources directly to the battery and let them get on with the job!
Cheers
John | J and V
"Not everything that can be counted counts, and not everything that counts can be counted."
- Albert Einstein
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