Chinook RV Forum

It is currently September 22nd, 2017, 12:09 am

All times are UTC - 8 hours




Post new topic Reply to topic  [ 23 posts ]  Go to page Previous  1, 2, 3
Author Message
PostPosted: July 23rd, 2017, 9:52 am 
Offline
User avatar

Joined: October 20th, 2015, 6:57 am
Posts: 526
Location: Northern NJ
I read an internet thread where someone called Lifeline, and was told the PD charger was pretty optimal for their batteries.

I guess I see what you're saying about the voltage, but it still sounds to me like they're saying bulk mode is 14.4 up to 90% SOC, then it drops to 13.6 for what could be called absorption for hours, and then finally later on to the typical 13.2 float. Chart from PD:
Attachment:
File comment: PD charger voltage profile
image.gif
image.gif [ 47.02 KiB | Viewed 64 times ]

Now here's something that I really don't understand:

The other day I replaced my fridge's scorched power board with a Dinosaur board, and also added a new DC heating element.

Now we all know that using the DC mode is a battery killer at ~14 amps. But I figured, hey, I'm on shore power with a 45 amp capable PD converter-charger, so no problem doing a test run. After all, I can run fans and lights and the converter handles it all while the coach battery sits at a zero discharge rate.

But whenever I put the fridge into DC mode, my battery monitor instantly shows a 4 amp discharge! Which seems to tell me that the PD is only contributing 10 amps of DC. Wth?

EDIT: so later I tried again for longer, wondering if maybe the PD thought a battery was charging and it had to limit amps or something. After about a minute, the battery discharge rate had dropped to 2.2 amps, but I think it still should've been zero.

_________________
1994 Concourse, wood & heated tile floor, tin ceiling, custom lighting


Last edited by kdarling on July 23rd, 2017, 1:36 pm, edited 1 time in total.

Top
 Profile  
Reply with quote  
background-color: #C1CAD2
 

PostPosted: July 23rd, 2017, 10:22 am 
Offline
User avatar

Joined: July 31st, 2014, 1:01 am
Posts: 1828
Location: 1999 Concourse
Yes the voltage outputs of the PD charger look very close to a match for what Lifeline calls for.... at 77ºF. That's the potential catch. If your batteries are at a temperature other than 77ºF, the voltages called for are different (higher when colder; lower when hotter). Especially with the batteries in an outside compartment, there could be some big temperature swings. Even for mine, which are inside under the couch, they are typically quite a bit colder than 77ºF in the morning hours, when the charging tends to occur (using solar).

As far as I know the PD charger does not have available temperature compensated charging, so it won't be "right on" unless the batteries are at 77ºF. When a charger does have temp comp functionality, it's just a matter of attaching a small ring terminal or sensor to the battery post or case (depending on the style). The the charger's built in temp comp function will add or subtract at a certain rate (usually adjustable to match the rate the batteries want) so that the voltage is the *equivalent* of those original voltage settings at whatever temps the batteries are actually at. This might be 13.7 (vs. 14.3) if they are hot, or 15.0 (vs. 14.3) if they are cold. Since tenths of a volt count, it's a fairly large difference.

That's not to say there's no place for the PD charger. To my mind it's just about knowing what given charger can and can't do, and then deciding how it fits your use case/philosophy/etc.

Here is a chart showing the effect of temperature on charging voltage requirements (to be equivalent to the suggested ones at 77ºF). This is from the Lifeline Battery Manual.

Attachment:
voltage vs. temp.png
voltage vs. temp.png [ 64.4 KiB | Viewed 62 times ]

_________________
1999 Concourse


Top
 Profile  
Reply with quote  
PostPosted: July 24th, 2017, 10:06 am 
Offline

Joined: October 12th, 2015, 5:54 am
Posts: 223
Location: Santa Cruz
kdarling wrote:
But whenever I put the fridge into DC mode, my battery monitor instantly shows a 4 amp discharge! Which seems to tell me that the PD is only contributing 10 amps of DC. Wth?

EDIT: so later I tried again for longer, wondering if maybe the PD thought a battery was charging and it had to limit amps or something. After about a minute, the battery discharge rate had dropped to 2.2 amps, but I think it still should've been zero.


I think it should have been zero as well. Curious.... doesn't 14 amps sound a bit low for an electric heating element? That's less than 200w which just doesn't sound like much to me. But even if it's twice that, I would hope your charger would assume full duty of supplying power due to it's 45 amps rating.

What happens when you disconnect the bank?

_________________
1994 Premier


Top
 Profile  
Reply with quote  
Display posts from previous:  Sort by  
Post new topic Reply to topic  [ 23 posts ]  Go to page Previous  1, 2, 3

All times are UTC - 8 hours


Who is online

Users browsing this forum: No registered users and 2 guests


You cannot post new topics in this forum
You cannot reply to topics in this forum
You cannot edit your posts in this forum
You cannot delete your posts in this forum
You cannot post attachments in this forum

Search for:
cron
Powered by phpBB® Forum Software © phpBB Group