Thanks for contributing your first post, and welcome to the Forums.
You sound like an incredibly patient and caring person. From what you've written in your post, it seems like you're pretty clear with knowing your boundaries: You are ok to supportive him during his mood, but the lying is not ok.
Is this something that you've had a chat about? If so, how did it go?
I think confronting him when is not in a great frame of mind is wise. Choosing your timing when you are both feeling calm can be helpful. Another thing that might be helpful is to remember to identify him as a person, not as the illness. Within this, are behaviours and symptoms. I say this because little nuances in how we use language like, 'he is bipoloar' can sometimes overlook the other characteristics that make that person who they are.
Regardless of his illness, lying is a behaviour that is having an impact on you. Naming this (and providing clear examples of when he has lied), and describing it's impact (how it's made you feel) can be a way of raising his awareness of his actions. Relationships Australia has some resources about how to have conversations that might be useful.
We've also had a new member @KatieG join the Forums today, who also having some difficulties caring for her partner who has MI. You can read about it here. Also @mountain also had/has a partner with bipolar. You might find reading their experiences helpful. Feel free to contribute to their threads too.
Again, welcome to the Forums!
Hope to see more of you around.
CB
Hi @BPBear
What I meant when I wrote: 'I think confronting him when is not in a great frame of mind is wise,' is to choose your timing as best you to have a potentially difficult conversation with your loved one. Ensure that both you and them have as best a capacity to be able to participate in the conversation together. For instance, if either of you are in a low mood, or feeling exhausted, agitated or rushed etc, perhaps wait until the both of you are in better state of mind.
Now, this might be tough if either of you feel continual not 100% - that's ok. What we're trying to do, is just decrease any further stress before having a tough discussion. Perhaps pick a time of the day where both of you feel better. For instance, I know for me, I feel as my best in the morning after breakfast, as with my loved one. So I could plan to have a conversation with them around this time.
The reason I suggest this is having a potentially difficult conversation when you're feeling well equips both of you with with a greater capacity to speak openly rather than defensively. I hope this makes sense. Happy to expand if not. 
Help us push aside the stigma and discrimination surrounding complex mental health and change the way people talk about, and care for, mental illness.
SANE acknowledges the Traditional Owners of Country throughout Australia and recognises the continuing connection to lands, waters and communities. We pay our respect to Aboriginal and Torres Strait Islander cultures; and to Elders past and present.
SANE values diversity. We are committed to providing a safe, culturally appropriate, and inclusive service for all people, regardless of their ethnicity, faith, disability, sexuality, or gender identity.
Help us push aside the stigma and discrimination surrounding complex mental health and change the way people talk about, and care for, mental illness.
SANE acknowledges the Traditional Owners of Country throughout Australia and recognises the continuing connection to lands, waters and communities. We pay our respect to Aboriginal and Torres Strait Islander cultures; and to Elders past and present.
SANE values diversity. We are committed to providing a safe, culturally appropriate, and inclusive service for all people, regardless of their ethnicity, faith, disability, sexuality, or gender identity.