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otrfun
On The Road
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Forgot to mention this previously. Something that needs to considered when electing to turn on a dc to dc charger based on ignition voltage (vs. alternator output voltage) is potentially reduced current to the starter while starting the engine. As soon as the ignition is turned on, a 40a dc to dc charger could be drawing as much as 60a from the battery. On some vehicles that 60a reduction could impact starter performance---especially in extreme cold/hot weather conditions.
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Teleman
Clayton, CA, USA
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otrfun wrote:Forgot to mention this previously. Something that needs to considered when electing to turn on a dc to dc charger based on ignition voltage (vs. alternator output voltage) is potentially reduced current to the starter while starting the engine. As soon as the ignition is turned on, a 40a dc to dc charger could be drawing as much as 60a from the battery. On some vehicles that 60a reduction could impact starter performance---especially in extreme cold/hot weather conditions.
As I recall there is a delay from when the ignition is activated to when the charger passes current.
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S Davis
Western WA
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Teleman wrote:otrfun wrote:Forgot to mention this previously. Something that needs to considered when electing to turn on a dc to dc charger based on ignition voltage (vs. alternator output voltage) is potentially reduced current to the starter while starting the engine. As soon as the ignition is turned on, a 40a dc to dc charger could be drawing as much as 60a from the battery. On some vehicles that 60a reduction could impact starter performance---especially in extreme cold/hot weather conditions.
As I recall there is a delay from when the ignition is activated to when the charger passes current.
Delay is about 30 seconds and then it ramps up the amps over about another 30 seconds.
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otrfun
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S Davis wrote:Teleman wrote:otrfun wrote:Forgot to mention this previously. Something that needs to considered when electing to turn on a dc to dc charger based on ignition voltage (vs. alternator output voltage) is potentially reduced current to the starter while starting the engine. As soon as the ignition is turned on, a 40a dc to dc charger could be drawing as much as 60a from the battery. On some vehicles that 60a reduction could impact starter performance---especially in extreme cold/hot weather conditions. As I recall there is a delay from when the ignition is activated to when the charger passes current. Delay is about 30 seconds and then it ramps up the amps over about another 30 seconds. Our Renogy draws max current almost immediately.
IMO alternator voltage should be the preferred turn-on method for any dc to dc charger. Using this method, the dc to dc charger cannot activate unless the alternator is online, providing charge voltage/current. This makes it virtually impossible for the dc to dc charger to inadvertently discharge the battery---even if you accidently left the ignition on (without the engine running) for several minutes, or much longer. For me, it's one less thing to worry about---a good thing.
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BFL13
Victoria, BC
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Good point about turning on the DC-DC with the engine off. Never thought of that possibility. I have my Renogy getting its 12v signal (switchable on /off) from the camper not from the truck. Not convenient to get that from the truck.
So idea is to use the DC-DC with the truck engine running, but seeing the above posts, the DC-DC in the camper could be turned on with the truck not running. Have to beware of that.
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StirCrazy
Kamloops, BC, Canada
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otrfun wrote:
IMO alternator voltage should be the preferred turn-on method for any dc to dc charger. Using this method, the dc to dc charger cannot activate unless the alternator is online, providing charge voltage/current. This makes it virtually impossible for the dc to dc charger to inadvertently discharge the battery---even if you accidently left the ignition on (without the engine running) for several minutes, or much longer. For me, it's one less thing to worry about---a good thing.
I am installing mine on a ignition controled Upfitter switch. this way it will only go when the key is on AND the switch is turned on. that way if my batteries are close enough to full the solar can handle it I can leave it off, but if I had a few days of bad weather I can switch it on to give the solar a hand. If I forget its on and I turn the truck off it will shut off.
Steve
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otrfun
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BFL13 wrote:Good point about turning on the DC-DC with the engine off. Never thought of that possibility. I have my Renogy getting its 12v signal (switchable on /off) from the camper not from the truck. Not convenient to get that from the truck.
So idea is to use the DC-DC with the truck engine running, but seeing the above posts, the DC-DC in the camper could be turned on with the truck not running. Have to beware of that. Have you considered installing a battery isolator? We installed a BI right next to our 40a Renogy dc to dc charger in our truck camper. It's a very simple install and you never have to remember to do anything (switches, ignition, etc.). It will also automatically prevent your dc to dc charger from discharging your TV battery if your alternator fails while driving in the middle of nowhere on an interstate somewhere.
You can place the BI relay inline with the primary power input to the dc to dc charger, or place the BI relay inline with the Renogy 12v ignition/trigger terminal. In either configuration, the Renogy will never turn-on unless the sensor wire on the BI detects >13.3v. >13.3v will not be present unless the alternator is on-line, operating. If the alternator goes off-line for any reason (failure or engine not running), voltage will drop below 13.3v forcing the BI to remove power to the dc to dc charger. Simple. Reliable.
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otrfun
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StirCrazy wrote:I am installing mine on a ignition controled Upfitter switch. this way it will only go when the key is on AND the switch is turned on. that way if my batteries are close enough to full the solar can handle it I can leave it off, but if I had a few days of bad weather I can switch it on to give the solar a hand. If I forget its on and I turn the truck off it will shut off.
Steve If I understand your install correctly, you shouldn't need to remember to do or switch anything if you install a battery isolator. The only caveat I can think of is the possibility the combined charge current from your dc to dc charger and solar exceeds the charge current capability of your batteries. Then, yes, you may want to manually switch one or the other off. Either way, a BI would still 100% protect you from TV battery discharge---even if you inadvertently left the Upfitter and ignition switch on, with the engine not running. Without the BI your dc to dc charger would discharge your TV battery.
We've had a BI, dc to dc charger and solar hooked up in our truck camper for 9 months with no issues. Works silently in the background. No need to remember any switch settings. If the alternator goes off-line for any reason (failure or engine not running), the dc to dc charger won't work.
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StirCrazy
Kamloops, BC, Canada
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otrfun wrote:StirCrazy wrote:I am installing mine on a ignition controled Upfitter switch. this way it will only go when the key is on AND the switch is turned on. that way if my batteries are close enough to full the solar can handle it I can leave it off, but if I had a few days of bad weather I can switch it on to give the solar a hand. If I forget its on and I turn the truck off it will shut off.
Steve If I understand your install correctly, you shouldn't need to remember to do or switch anything if you install a battery isolator. The only caveat I can think of is the possibility the combined charge current from your dc to dc charger and solar exceeds the charge current capability of your batteries. Then, yes, you may want to manually switch one or the other off. Either way, a BI would still 100% protect you from TV battery discharge---even if you inadvertently left the Upfitter and ignition switch on, with the engine not running. Without the BI your dc to dc charger would discharge your TV battery.
We've had a BI, dc to dc charger and solar hooked up in our truck camper for 9 months with no issues. Works silently in the background. No need to remember any switch settings. If the alternator goes off-line for any reason (failure or engine not running), the dc to dc charger won't work.
ya I was thinking that with the dc to dc charger you don't need an isolater as it basicly is one, if its off there is no passthrough if its on then you get charging. the reason I want to be able to manualy turn it off is more to take strain off the altanator when it isn't nessasary. so I would be treating my dc to dc charger as an emergency power sourse only. so if it has been cloudy and I am getting a lousy charge from the panels I can turn it on while I am driving to help out and so on..
Steve
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otrfun
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StirCrazy wrote:ya I was thinking that with the dc to dc charger you don't need an isolater as it basicly is one, if its off there is no passthrough if its on then you get charging. the reason I want to be able to manualy turn it off is more to take strain off the altanator when it isn't nessasary. so I would be treating my dc to dc charger as an emergency power sourse only. so if it has been cloudy and I am getting a lousy charge from the panels I can turn it on while I am driving to help out and so on..
Steve What size alternator? What size dc to dc charger do you use, or plan to use? It should be safe to leave a 20a dc to dc charger on full-time in most smaller vehicles. Most of the Renogys have a half-power mode. You could use a 40a unit in 20a mode for now. If you upgrade to a vehicle with a larger alternator in the future, you could switch back to 40a. Or, you might find your current vehicle will handle 40a just fine. Bottom line, it gives you some choice, flexibility.
We don't use our 40a Renogy for backup/emergency power. It gets extremely hard use during the summer when we're on the road. Use our 200ah lifepo4 to power our truck camper a/c when we take breaks. It only takes our a/c about 5-10 min to make the TC noticeable cooler---plus, no generator setup/startup or rumble. Once back on the road the dc to dc charger goes to work. Usually stop for a break after 1.5 - 2.0 hours of driving, which is about the time the dc to dc charger needs to top-off the lifepo4 again. On any given summer travel day the Renogy gets a *lot* of use---as much as 6 hours at max current. The lifepo4 works hard, too---after 9 mo. already approaching 40 cycles.
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