Jump to content

Will alternator parallel charging interfere with dual MPPT regulator?


Recommended Posts

Hi. I have just bought a Carpenter 29 and I plan to install solar. It currently charges the starter and house batteries (both single lead acid) from the alternator using what appears to be a simple relay that connects them in parallel when the engine is running. I would like to charge both batteries from solar and plan to use a dual MPPT regulator such as the EPever Duoracer https://aasolar.co.nz/product/duoracer-series-mppt-dual-battery-solar-charge-controller-10-30a-by-epever/

Will it cause a problem for the solar when the relay connects the batteries in parallel whilst the engine is running?

Cheers

Link to post
Share on other sites

I have a similar set up with Blue Seas VSR controlling the alternator charge, and a Victron MPPT reg doing the solar , have been pleasantly surprised that the VSR also links under strong sunlight solar charge. 

Link to post
Share on other sites

No problem, it'll work fine. Personally though, I'd go for a Victron controller over EPEver. More reliable, better interface, more programmable, and better output. 

Link to post
Share on other sites
On 27/10/2022 at 9:15 AM, waikiore said:

I have a similar set up with Blue Seas VSR controlling the alternator charge, and a Victron MPPT reg doing the solar , have been pleasantly surprised that the VSR also links under strong sunlight solar charge. 

Vsr's dont care where the voltage comes from, if it's high enough they will engage. They are available in single and dual sense (single watches one batt voltage for switching, dual watches both/either.)

Link to post
Share on other sites

In order to future proof for the possibility of dissimilar batteries, does a dc-dc charger (instead of the VSR) also work both ways? 

My original plan of a dual solar regulator was because they allow the house bank to be specified for the correct charge profile and then trickle charge a lead acid started battery through the 2nd connection. If I were to upgrade the house bank at some stage then the dual regulator allows that to be specified correctly. But if I go the VSR path then both batteries have to be charged with the same profile.

Link to post
Share on other sites

Think about this. The LiFePo4 battery does not want (or like) to be kept fully charged. The Lead Acid MUST be kept fully charged for decent life. Standby voltage for a LiFePo4 batt is around 13.4v, which conveniently is pretty close to the float voltage of an AGM. So a VSR is OK, but normally I put a switch in their circuit  so they can be manually disconnected when needed. 

Most DC-DC chargers have an input and output, so no, not bi-directional.

Link to post
Share on other sites

Some DC DC chargers will trickle charge the start battery when they have excess energy and the house battery is finished charging.

The CTEK 250SE is one such unit which includes a MPPT for solar.  Coupled with the CTEK 120S this is a pretty good solution for a Lead Acid bank.  But it is pricy.

I highly suspect you already have dissimilar batteries?  Probably a Starter and a Deep Cycle.  Most start batteries don't like being charged to 14.7v while most deep cycle batteries need to be charged to 14.7v.

I would certainly go DC/DC over VSR any day.

 

 

 

 

Link to post
Share on other sites
10 hours ago, CarpeDiem said:

Some DC DC chargers will trickle charge the start battery when they have excess energy and the house battery is finished charging.

The CTEK 250SE is one such unit which includes a MPPT for solar.  Coupled with the CTEK 120S this is a pretty good solution for a Lead Acid bank.  But it is pricy.

I highly suspect you already have dissimilar batteries?  Probably a Starter and a Deep Cycle.  Most start batteries don't like being charged to 14.7v while most deep cycle batteries need to be charged to 14.7v.

I would certainly go DC/DC over VSR any day.

 

 

 

 

I agree, why mix old and new tech, Just use a DC-DC charger, I'll be retrofitting one to my own Carpenter 29 next season with a smart shunt, BMS and Battery protect. We have the same batt set up as yours for now but with the new kit  its also future proofed for Lithium. I use Victron , its pricey but of good quality and well supported, there are other good brands too but whatever you use its best to stick with one brand as these days they all talk to each other with digital smarts.

Link to post
Share on other sites

Just keep this in mind. Some installs Ive seen, the alternator charges the start batt, DC-DC charges the LiFePo4. Technically OK, BUT you loose the main (IMO) advantage of LiFePo4 in that most DC-DC chargers dont have anywhere near the output of a decent alternator, so you bank charges much more slowly.  Better, (also IMO) is to use a proper good alternator, with ext reg and temp sensing - for the ALT! to charge the LiFePo4 and then DC-DC to charge the Start and Accessory (Thrusters, winches etc) batts.

This is a very good doc on LiFePo4 - incl some basic setup diagrams https://marinehowto.com/drop-in-lifepo4-be-an-educated-consumer/

Link to post
Share on other sites

My original plan was to install a dual regulator. It isn’t described as a dc-dc charger but it seems similar in function. You program the house battery type so it can charge it correctly and it also trickle charges the starter battery which must be a lead acid profile. 
Votronic have had one of these for years and the EPever one I was considering is newer: https://aasolar.co.nz/product/duoracer-series-mppt-dual-battery-solar-charge-controller-10-30a-by-epever/

It is about half the price of a dc-dc charger. Any thoughts on the pros and cons?

 

Link to post
Share on other sites

There's lots of different ways to approach this and what you should do now depends on where you want to be in the future.

I don't think you will get the optimal effect with a VSR and a start charger.  You'll find that when charging the start battery, the vsr will engage and now the charger will see both batteries and any substantial house loads, like a winch will pull down your start battery unnecessarily.

If you want to go down this path then you ideally need to ensure that the vsr kicks in above the voltage of the start charger.  You might find that's too high for your alternator...  Or use an diode isolator instead of the VSR which would be better in this application. 

Using an mppt as a dcdc charger comes with some complications.  Most mppt chargers, incl the epever, will only buck convert so you can't use them as a dc dc charger where the input voltage is the same.  Maybe if you had a 24v start system, then it could work as a dcdc charger, but I would never recommend it because some MPPT controllers (victron), short circuit the PV side by design in certain error conditions.  And obviously short circuiting your start battery and alternator would be #verybad. 

I use a constant current dc power supply attached to the MPPT input as a shore charger when I have no solar panels on board. The power supply is short circuit protected and outputs max 18v DC @ 17amps which is below the input spec of the MPPT. 

Link to post
Share on other sites

Thanks everyone for sharing their thoughts. I have just ordered a Renogy DCC30S from Burnsco https://www.burnsco.co.nz/catalog/product/view/id/29011/s/dc-battery-charger-reg-renogy-30a/category/2/

It’s an MPPT and DC-DC charger so it should cover my needs of charging both batteries from solar and the alternator. It can charge different profiles of house battery and trickle charge the lead acid starter. Similar to the CTEK but a bit cheaper. And I can remove the exisiting relay that did the parallel charging before (on closer inspection the connectors on the relay had got hot enough to melt the plastic so I’m glad to have that gone).

Cheers

Link to post
Share on other sites

Hmm, you might like to consider this from the Facebook Marine Electrics forum admin, Rod Collins. I consider Rod one of the world experts in this field (bold and underlined by me);

WE are now allowing used electrical gear to be sold in the group..
WARNING:Only legit Marine brands EG: Victron, Magnum,Outback, BLUESEA SYSTEMS Ancor Balmar, Mastervolt Sterling Power, Pro Mariner.etc. No Pop-up/phony"brands" that masquerade as quality products such as Renogy, Scamzon electrical parts etc. etc..No Noco products. No used LiFePO4 batteries unless a quality brand such as Lithionics, Mastervolt,orVictron, (Battleborn would be the lowest quality allowed.) No DIY …
 
Link to post
Share on other sites

Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.
Note: Your post will require moderator approval before it will be visible.

Guest
Reply to this topic...

×   Pasted as rich text.   Paste as plain text instead

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.

×
×
  • Create New...